SYDNEY — An Australian couple denied they had abandoned their son with his Thai surrogate after learning he had Down syndrome, saying in an interview broadcast on Sunday that the woman demanded she be allowed to keep the boy.

Baby Gammy's surrogate mother, Pattaramon Chanbua, a 21-year-old food vendor with two young children of her own, had accused the boy's biological parents, Wendy and David Farnell, of leaving her with the infant while taking his healthy twin sister, Pipah, back with them to Australia.

"We did not abandon our son," an emotional David Farnell said in an interview with Australia's "60 Minutes."

"(Pattaramon) said that if we tried to take our little boy, she's going to get the police and she's going to try and take our little girl and she's going to keep both of the babies," he said.

Pattaramon denied that she'd ever threatened to keep both children, but agreed that she hadn't wanted the Farnells to take Gammy home.

"I did not allow Gammy to go back with them — that's the truth," she told The Associated Press on Sunday, apparently backtracking from her earlier accusation that the couple had abandoned the baby boy. "It is because they would have taken Gammy back and put him in an institute."

The case, which has focused global attention on the largely unregulated surrogacy industry in Thailand, became even murkier when it emerged that David Farnell had been convicted in the 1990s of multiple sex offenses against young girls. Farnell insisted Sunday that his daughter is not at risk of harm from him.

The Farnells had been trying for eight years to conceive when they approached a Thai surrogacy agency for help.

David Farnell, who has three children from a previous relationship, said the problems began when they found out before the twins' birth in December that the boy would have Down syndrome. The couple was angry that the surrogacy agency had not conducted tests earlier that could have detected the condition, because by the time they found out, it was too late in the pregnancy to abort the fetus. Had they known earlier, they probably would have terminated the pregnancy, David Farnell said.

"I don't think any parent wants a son with a disability," he said. "Parents want their children to be healthy and happy."

They expected the surrogacy agency to give them a refund and find a solution. That's when the still-pregnant Pattaramon offered to keep Gammy, Farnell said.

"So we were thinking, oh, maybe — maybe — this might be OK," he said.

When the babies were born, however, the Farnells said they realized they wanted to keep both. But Pattaramon then insisted she be allowed to keep Gammy, and threatened to keep Pipah as well, David Farnell said. The couple believes Pattaramon wanted to keep Gammy because male children are prized in Asian cultures.

The Farnells said they never went to any officials or contacted the Australian Embassy in Bangkok about Pattaramon's alleged threat. They left Gammy and returned home to Western Australia state only with Pipah, they said, because their visa was running out.

They didn't apply for a visa extension because they wanted to get Pipah to Australia to keep her away from Pattaramon, David Farnell said. Their plan was to fight to get their son back by going through the Australian authorities, he said.

In the six months they have been back in Australia, however, they have never contacted the authorities about their son, because they say they still feel their daughter is at risk of being taken back by Pattaramon. They have never called to check on Gammy's welfare, and have contacted a liaison between themselves and Pattaramon only once, David Farnell said.

"It has been very stressing," he said. "We miss our little boy. I come home from work some days and Wendy has dressed our little girl all in blue because she wants still to remember the little boy."

Asked about his history as a sex offender, Farnell said he no longer feels any urges to sexually assault young girls and insisted Pipah would be safe in his care.

"I will do everything in the world to protect my little girl," he said. "I have no inclination of doing anything like this. I don't have any thoughts about this at all. That is the 100 percent truth. I cannot do this again."

Farnell rejected the suggestion that his predilection for young girls had influenced his decision to bring home his daughter and not his son.

"I'm actually ashamed you would say something like that," a tearful Farnell said. "Honestly, there is no reason to be concerned. I'm not going to harm my little girl."

"Everybody hates sex offenders — they're the lowest form of people, not even worthy of breathing," he added. "I know that. That's why I've tried so hard and wanted to be a good father for my children so that at least the people can see that I am a good person now."

The executive producer of "60 Minutes," Tom Malone, said the Farnells were not paid for the interview, but acknowledged that the program had made a donation to a charity raising money for Gammy's care.

An Australian couple denied they had abandoned their son with his Thai surrogate after learning he had Down syndrome, saying in an interview broadcast on Sunday that the woman demanded she be allowed to keep the boy.